The abdomen contains the muscles that most beginners struggle with because they take a long time to develop and need a low level of body fat to be seen. The abdominal muscle group consists of three main muscles:
1. Rectus abdominis - commonly known as the abs, this is a large flat muscle wall that runs from the lower chest to the pubic bone.
2. Obliquus abdominis - commonly known as the obliques, this muscle runs diagonally along the side of the mid-section from the lower ribcage to the pubic area. The internal obliques lie underneath the external obliques.

3. Transversus abdominis - this is a thin strip of muscle that runs horizontally across the abdomen.
You can target these muscles effectively by performing the following exercises:
1. Crunches - 3 sets of 15-20 reps. This exercise will work the upper abs.

2. Pelvic tilts - 3 sets of 15-20 reps.This exercise will target the lower portion of the abdomen below the navel.
3. Side bends - 3 sets of 15-20 reps. This exercise will work the obliques.
As with all exercises you need to take care in scheduling specific body parts. To begin with you should incorporate your abdominal exercises into a program similar to the one suggested below:
Day 1: Biceps, Back, Abs
Day 2: Hamstrings, Shoulders, Abs
Day 3: Quads, Forearms, Calves
Day 4: Triceps, Chest, Abs
For the first couple of weeks complete one set but then add one set each week to a maximum of three. At the end of three months you will be ready to move on to more intensive intermediate level exercises.